ALERT: Geomagnetic K-index of 4 Alert issued on April 26

A Geomagnetic K-index of 4 Alert was issued by NOAA’s Space Weather Prediction Center on April 26, 2026. The alert indicates that geomagnetic activity reached a K-index of 4 during the synoptic period from 03:00 UTC to 06:00 UTC on April 26. The alert remains active, signaling elevated, but not storm-level, geomagnetic conditions.

Areas primarily poleward of 65 degrees geomagnetic latitude are subject to weak power grid fluctuations. Aurora may be visible at high latitudes, including regions such as Canada and Alaska. These impacts are in line with NOAA’s official guidance for a K-index of 4 event.

Forecasts attribute the recent geomagnetic activity to the arrival of a transient solar wind structure, likely a glancing blow from a Coronal Mass Ejection (CME) that departed the Sun on April 23. Solar wind conditions during the period included enhanced magnetic field strength reaching 12 nT and an increase in solar wind speed to 450 km/s. Additional geomagnetic activity is anticipated as further glancing influences from CMEs are expected to arrive between April 26 and April 27, 2026.